Method of manufacturing bags

ABSTRACT

The present invention provides a method of manufacturing bags from a strip-like bag material of a thermoplastic synthetic resin and is characterized by having the heat-sealing of the bag material and the severing of the heat-sealed portions performed in two separate steps to thereby secure the smooth transfer of the bag material so that the bag manufacturing efficiency may be enhanced.

United States Patent Torigoe (451 July 11, 1972 [54] METHOD OFMANUFACTURING BAGS [56] References Cited [72] Inventor: YasuhiroTorigoe, c/o Taiyo Shokai Co. UNITEDSTATES PATENTS Ltd-a 4 ChomeKiwkoiwa 3,146,!47 8/I964 Naser ..93/& R ux 8 Y- Japan 3,057,521 [0/1962Hannon ..225/|00 22 Filed: July l 970 3,447,990 6/1969 F088 .225/l00 UX[2|] Appl. No.: 51,472 Primary Examiner-Demand Stickney AnomeyPolachek &Saulsbury [30] Foreign Application Priority Data 57 ABSTRACT July 5,I969 Japan A l/52813 The present invention providcs a method fmanufacturing bags from a strip-like bag material of a thermoplasticsynthetic [52] U.S. Cl. .93/35 R, 93/8 R, 225/100 resin and ischaracterized by having the heat-sealing of the bag [51] Int.Cl .v..........v...............B3lb49/04 material and the severing of theheat-sealed portions per- [58] Field ol Search ..93/8 R, 35 R;225/l00 fd in two separate steps to thereby secure the smooth transfer of the bagmaterial so that the bag manufacturing efficiency may be enhanced.

lClainn8DnwingFigures PATENTEDJUL 1 1 I972 3. 675 542 sum 1 or 3INVENTOR. YASUHIRO TORIGOE BY PATENTEDJuL 1 1 m2 3. s75 542 SHEET 20$ 3INVENTOR.

YASUHIRO TORI GOE Quid/W 2 roe/v5 PA'TENTEDJUL 1 1 m2 SHEET 3 BF 3INVENTOR.

YASHIRO TORIGOE METHOD or MANUFACTURING mos SUMMARY OF THE INVENTION Thepresent invention is concerned with a method of and machine forcontinuously manufacturing bags from a strip-like bag materialconsisting of a folded film or a tube of a thermoplastic synthetic resinsuch as vinyl or polyethylene, and more particularly, it relates to amethod of and machine for manufacturing side-sealed bags having weldedside edges.

In general, in conventional methods and machines in the art, the bagsare produced in such a way that the strip-like bag material is placed ona belt conveyor on which the side edges thereof are heat-cut andconcurrently heat-sealed by the use of a heat-sealer. With such knownmethods and machines, however, the divided individual bags are merelyresting on the conveyor. Therefore, in case the conveyor is of the typewhich is operated intermittently, the positions of these individual bagswere often displaced owing to their inertia or to air re sistance towhich the bags are subjected, or the bags tended to adhere to thesurface of the conveyor belt at their fused portions. Thus there asrequired the provision of additional equipment for correcting theirregular positions of the individual bags and for removing the adheredbags on the conveyor means to be transferred thereon continuously. Also,since the heat-cutting and welding were performed at the same time insuch known methods and machines, there arose the inconvenience anddifficulty in obtaining uniform degree of welding in the heat-sealedportions. Thus, it has been impossible to manufacture bags at highspeed.

It is, therefore, an object of the present invention to eliminate thedrawbacks and inconveniences of the prior art and to provide a newmethod of and machine which improve the mechanical strength of thewelded portions and which secure the smooth transfer of the bag materialto enhance the bag manufacturing efficiency by having the welding andsevering of bags performed in two separate steps.

The method of the present invention comprises the following three stepswhich are performed sequentially. That is to say, it comprises a firststep in which a strip-like bag material consisting of a folded film or acollapsed tube of a thermoplastic synthetic resin is heat-sealedtransversely across said bag material by a heat-sealer and at the sametime an easily severable linear fragile region is formed across theentire breadth of said material along the center line of the heatsealedportion thereof; a second step in which the heat-sealed bag material isconveyed for a distance corresponding to at least the length of a singlebag for cooling the heat-sealed portion; and a third step in which thebag material thus processed is pulled in opposite directions to beseparated into individual bags at the linear fragile region thereof.

The machine of the present invention comprises: a first intermittentlyoperated conveyor means having a pair of nipping means and adapted tointermittently convey the strip-like bag material consisting of a foldedfilm or a collapsed tube of a thermoplastic synthetic resin; aheat-sealer provided on the material-feeding side of said first conveyormeans and being operable, at each inoperative interval thereof, to presssaid bag material against the surface of a supporting table to heatsealthe same, said heat-sealer having a welding face having a shape suitablefor heat-sealing said bag material transversely in cooperation with thesupporting table and also suitable for forming a central fragile linearregion in the heat-sealed portion of the bag material; a guide rollerprovided between said heat-sealer and said first conveyor means andcapable of effecting vertical displacement; and a second continuouslyrotatable conveyor means of nipper type provided on the delivery side ofsaid first conveyor means.

The method and the machine according to the present invention willhereunder be described in further detail with respect to preferredembodiments in conjunction with the accompanying drawings in which:

FIG. I is a perspective view of a bag material being processed into bagsaccording to the present invention;

LII

FIGS. 2 through 4 are diagrammatic representations, showing the processof and machine for manufacturing bags as one embodiment of the presentinvention;

FIG. 5 is an enlarged view of an intermittently operated conveyor means;

FIG. 6 is a vertical cross-sectional view taken along the line AA ofFIG. 5; and

FIGS. 7 and 8 are diagrammatic representations, showing two otherembodiments of the machine according to the present invention.

Referring to FIGS. 2 to 4, there is shown a bag-making machine embodyingthe present invention. The machine is provided with an intermittentlyoperated conveyor means a of a nipper type which comprises a pair ofintermittent rollers ll and 12, a pair of relatively small rollers llaand 12a provided on the delivery side of the conveyor means and aplurality of endless belts 13 and 14 each having a small circularcross-section. The upper and lower belts l3 and 14 pass over the rollerII and its mating smaller roller 11a and the roller l2 and its matingsmaller roller 12a, respectively in the manner depicted in FIG. 6.

Indicated by reference numeral 15 is a supporting table provided on thefeeding side of said intermittently operated conveyor means a andbeneath the path of said bag material. Numeral 16 represents aheat-sealer arranged to be brought into contact, at its welding edge,with the upper surface of said supporting table 15 and to be moved awaytherefrom at each inoperative interval of the conveyor means a. Thisheat-sealer 16 has a welding face in the form of a slightly dull-angledknife edge.

Numeral 17 indicates a guide roller located between the intermittentconveyor means a and the supporting table 15 and arranged to bevertically displaceable relative to the frame of machine, not shown.Indicated by 17' is another guide roller which is fixed below thevertically displaceable guide roller 17.

Indicated by b is another conveyor means of a nipper type having aplurality of endless belts 18 and 19 similar to those of the firstconveyor means a. As shown, the second conveyor means b is located onthe delivery side of said first conveyor means, and is arranged to becontinuously rotated. It should be understood that the second conveyormeans b may be substituted by a pair of oppositely disposed continuouslyrotatable rollers.

When it is desired to operate the machine according to the presentinvention, the bag material 10 consisting of a folded film or acollapsed tube of a thermoplastic synthetic resin such as polyethyleneor polypropylene is fed to pass over the supporting table 15 andtherefrom to pass around the guide rollers l7 and 17 and then to passbetween the pair of intermittent rollers 11 and 12 of the first conveyormeans a, and therefrom to pass between the upper and the lower endlessbelts l8 and I9 which are to be rotated continuously.

After the loading of the strip-like bag material on the machine, theintermittently operated conveyor means a is operated to convey the bagmaterial intermittently for a certain distance at a time correspondingto the length of a single bag. During each inoperative interval of theconveyor means a, the heat-sealer 16 having a knife-edge is lowered toheatseal the bag material transversely in cooperation with the uppersurface of the supporting table 15 to thereby form a welded portion 20and also to form a fragile region 21 along the center of said weldedportion.

Then, the bag material 10 thus processed is further conveyedintermittently. The position of the guide roller 17 is adjusted so thatthe feeding of the bag material 10 will be halted in such a way thatsaid welded portion 20 will be positioned midway between theintermittent conveyor means a and the second conveyor means I: at theend of one feeding action or at the end of every several feeding actionsof said first conveyor means.

When the machine is operated continuously, the bag material 10 which hasbeen heat-sealed by the heat-sealer I6 as depicted in the drawings istransferred by the intermittent conveyor means a. While said bagmaterial is conveyed, the welded portion 20 is allowed to cool andsolidify. Since the travel of said welded portion 20 stops between thefirst and second conveyor means a and b, the forward bag portion a ofthe bag material 10 is, at such a time, already nipped between the pairof conveyor belts l8 and 19 of said second conveyor means. Thus, theforward bag portion 100 is coercively pulled by these belts and, as aresult, the bag portion 100 is severed away along said fragile region 21from the adjacent bag portion and is delivered one after another as thefinished bags 10b onto the product-receiving table which is provided onthe delivery side of said second conveyor means.

FIG. 7 shows a modified example of the machine of the present invention,in which the supporting table of the preceding example is substituted bya rotatable drum 15a so that this drum rotates while carrying thereonthe bag material 10.

FIG. 8 shows still another example of the machine of the presentinvention, in which said drum 15a of the preceding example issubstituted by a belt conveyor 15b which also moves together with thebag material 10. These two examples of the machine will provide bettercooling effects of the welded portions and will insure no deformationsof the welded portions.

As may be seen from the foregoing, according to the method of thepresent invention, a series of bags that the bag portions can be easilyseparated from each other at the fragile regions 21, after the portions20 have been completely heatsealed, can be obtained. Also, there areobtained individual bags having tightly welded end edges at which thebag portions have been severed from each other and which give a goodappearance, In addition to the foregoing advantages, the presentinvention provides a further merit that, because the bag material 10 isnot cut apart at the time of welding, a continuous lengthy bag materialwith many bag portions can be formed. Furthermore, the bag portions areadapted to be severed from each other along the central fragile regions2] after the bag material has been transferred for a distancecorresponding at least to the length of a single bag. Accordingly,welding may be carried out sequentially even during the period of timeuntil the welded portions become cooled, and thus, the efficiency of bagmanufacture is enhanced substantially. What is more, the method of thepresent invention requires no cutting blades to sever the bag portions.

On the other hand, according to the present invention, even in the casewhere the welded portions 20 happen to adhere to the supporting table15, the bag material 10 can be quite easily detached from the surface ofthe supporting table since the bag portions remain to be continuousuntil they are separated. Also, because the severing of the bag portionsfrom the continuous bag material 10 into individual bags 10b isperformed by pulling one bag portion off the adjacent another one, themachine of the present invention does not require the provision of acutting device comprising a set of blades as have been required byconventional bag-manufacturing machines. This obviates the need foradditional operations such as the grinding and the replacement of theblades from time to time, thus markedly reducing the maintenance workand cost.

Furthermore, in the machine of the present invention, means fortransferring the bag material 10 and means for transferring theindividual bags 10b are independent from each other. This permits theselection of optimum conveying speed for each of these two kinds ofconveying devices independently of each other.

ln the embodiments illustrated, there is shown a guillotinetype cutter22 which is provided on the delivery side of the intermittent conveyormeans a. This cutter 22 is arranged to be operated when the continuouslyoperated conveyor means b is at rest. It is operatively connected tosaid intennittent conveyor means so that it can descend to assume itscutting position during the suspension of the operation of theintermittent conveyor means to cut apart the welded portion of the bagmaterial 10 and then to ascend to its normal position.

What l claim is:

l. A method of manufacturing bags comprising the steps of: heat-sealinga strip-like material transversely across the same by a heat-sealer andat the same time forming an easily severable linear fragile regionacross the breadth of said material substantially along the central lineof the heat-sealed portion thereof such that a series of interconnectedbags are formed, said strip-like bag material consisting of a foldedfilm of a thermoplastic synthetic resin; conveying the sealed strip-likebag material around the roller guides such that conveying direction issubstantially reversed; thereafter conveying the reversed directionmaterial around a roller-pulling means such that a pulling direction isimpartable to the material at an angle of at least about 90; thereafterconveying the heatsealed bag material for a distance corresponding to atleast the

1. A method of manufacturing bags comprising the steps of: heatsealing astrip-like material transversely across the same by a heat-sealer and atthe same time forming an easily severable linear fragile region acrossthe breadth of said material substantially along the central line of theheat-sealed portion thereof such that a series of interconnected bagsare formed, said strip-like bag material consisting of a folded film ofa thermoplastic synthetic resin; conveying the sealed strip-like bagmaterial around the roller guides such that conveying direction issubstantially reversed; thereafter conveying the reversed directionmaterial around a roller-pulling means such that a pulling direction isimpartable to the material at an angle of at least about 90*; thereafterconveying the heat-sealed bag material for a distance corresponding toat least the length of one of said bags; and pulling the bag materialthus processed by means of pinching rollers moving at a greater speedthan said roller pulling means such that a terminal bag being passedinto the pincher means is separated from subsequent approachingheatsealed bag material, the separation taking place at the linearfragile region thereof.